<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <h3>子页面</h3>

  <script>
    document.domain = "127.0.0.1"

    var data = '我是子页面的数据'
  </script>
</body>

</html>